Page 74 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

How does sunscreen work?

See how this clever substance protects our skin from harmful UV rays

he dangers of the Sun’s rays have
long been appreciated by humanity. Ultraviolent radiation
TThe ancient Greeks slathered The Sun produces three types of
radiation, but UVC is filtered out by

themselves with olive oil, while ancient the Earth’s ozone. Therefore, it isn’t
Egyptians used extracts of rice and jasmine responsible for skin damage.
that are still present in modern day
skincare products. UVA rays
Whether it is in the form of a spray, lotion, The amount of UVA
produced by the Sun is
gel or wax, modern sunscreen works by
constant throughout
combining ingredients that either block or UVB rays the day; large amounts
absorb the Sun’s dangerous ultraviolet (UV) UVB rays account for five per cent of will cause the skin to

rays. Minerals such as zinc oxide refl ect UV the Sun’s radiation and are what age and wrinkle.
rays directly, whereas organic chemicals causes the skin to burn.
such as avobenzone absorb UV radiation
into their chemical bonds, and then Protecting
gradually release it as heat. The Sun your skin
Sunscreen stops up to 97
Protection Factor, or SPF, indicates how well
per cent of the Sun’s rays
the sunscreen will block the Sun’s UVB from penetrating your
rays, which are responsible for burning the skin, by either refl ecting
skin. An SPF 15 sunscreen will prevent your or absorbing them.
skin from burning for 15 times longer than it The epidermis
usually takes for you to burn, but will only The epidermis
block out around 93 per cent of UVB rays. absorbs UVB rays that
will damage the
The chore of rubbing on sunscreen may lower layer, resulting
soon be a thing of the past, however. There in the eventual loss of
is currently a race to develop a pill that will The dermis the top layer.
provide full UV protection, based on a This layer absorbs UVA
compound produced by the algae that live rays, irritating the blood
vessels enough to make
inside coral. Scientists hope to see this
them swell and create
product for sale on the market in the the characteristic © Thinkstock
coming years. redness of sunburn.
Why do cats go crazy

for catnip?

The oil that stimulates a cat’s sensory neurons

here is an oil found in the catnip emotional responses to stimuli
plant (nepeta cataria) called (consequently causing a behavioural
Tnepetalactone. Researchers response), but also regulate
believe that when this oil enters a cat’s neuroendocrine responses, making the

nasal tissue, it binds to protein receptors cat react to an artificial cat pheromone. It
that stimulate sensory neurons. This doesn’t affect all cats, but many react by
leads to a response in neurons in a certain rolling around, flipping over, becoming

part of the brain known as the olfactory hyperactive and sometimes acting
bulb which projects to other brain aggressively, before experiencing a come
regions; regions that not only mediate down ten minutes later.

74 How It Works